One of the objectives of this project is to investigate the ultrastructure of the crustacean stretch receptor organ in relation to its function. We plan to investigate stretch-induced structural changes in the dendrities of the sensory neuron, where the generator potential occurs, by using ultraquick freezing and freeze-substitution methods. In addition, the membrane fine structure of the inhibitory synapses on the receptor neuron will be studied by using the freeze-fracture method. The other objective of this project is to investigate the ultrastructural and electrophysiological properties of newly-formed neuromuscular junctions in tissue culture. Also we will study the development of extrajunctional acetylcholine receptors in cultured muscle cells by using microelectrophysiological and freeze-fracture methods.